The present invention relates to a desiccating matrix and a method for applying the desiccating matrix in manufacturing insulating glass units. More particularly, the invention provides a non-adhering desiccating matrix for use with the insulating glass units, and includes a method of applying such non-adhering desiccating matrix to a spacer for an edge assembly of an insulating glass unit.
Insulating glass units (xe2x80x9cIGUsxe2x80x9d), made with at least two glass panels arranged in spaced-apart relationship with an edge assembly to form an enclosed interior space, require the presence of a desiccant in the interior space to avoid condensation of moisture or other volatile materials due to the temperature difference between the inner and outer glass panels. Such condensation is generally referred to as xe2x80x9cfoggingxe2x80x9d of the IGU. Moisture or materials such as volatile organic chemicals (xe2x80x9cVOCsxe2x80x9d) may remain in the interior space after manufacture or may seep into the interior space during post-manufacture use. The moisture and VOCs may cause fogging in the interior space. The desiccant is provided to remove the moisture and/or VOCs from the interior space by adsorption. As used hereinafter, the terms xe2x80x9cdesiccating materialsxe2x80x9d and xe2x80x9cdesiccantsxe2x80x9d include adsorbents of both moisture and VOCs, except where specific adsorbents of moisture or VOCs are separately identified and limited as to specific materials adsorbed.
In early IGUs, loose particles of desiccating materials in a container were placed in the interior space of the IGU, free of any matrix for holding together the desiccant particles. This resulted in problems such as spillage of the desiccating material from the spacer, bead migration and dusting, too-rapid adsorption of moisture resulting in premature saturation of the desiccant prior to assembly of the IGU and reduced life expectancy or premature failure of the IGU, and included problems in manufacture due to the size and nature of the particles of desiccant materials. An early example of such units may be found, for example, in U.S. Pat. No. 2,964,809. Similarly, in later IGUs, the loose desiccant material was disposed in the body of the spacer itself, such as is shown in U.S. Pat. No. 3,998,680.
Later IGUs were provided with a desiccant dispersed within a thermoplastic carrier, in which the thermoplastic was placed in the interior space, as shown, for example in U.S. Pat. No. 3,758,996. In an effort to simplify construction of the IGU, dimensionally stable sealant and spacer strips were developed. Such strips include an elongated ribbon of deformable sealant having an imbedded spacer means such as a corrugated metal strip. On the inner side of this strip is disposed a decorative facing which has impregnated therein a desiccant. Such a system is sold as SWIGGLE(copyright) Seal, and is disclosed in U.S. Pat. No. 4,431,691. Other IGUs include a spacer made of silicone or acrylic foam containing large quantities of a desiccant fill material, such as is shown in U.S. Pat. No. 4,950,344. An IGU with a spacer filled with a desiccating matrix is disclosed in U.S. Pat. No. 5,209,034.
Among other developments in this area are insulating glass units such as those shown in U.S. Pat. No. 5,177,916 and the progeny thereof, in which a U-shaped spacer is placed between glass panels to form an interior space, and an adhesive containing a desiccant is coated on the inside of the U-shaped spacer. A drawback of using mastics in an IGU like that described in U.S. Pat. No. 5,177,916 arises from limitations imposed by the mastic. The material may soften such that it sags at the temperatures to which the IGU is exposed in use. The desiccating mastic may evolve an excessive amount of water or organic vapors, which can result in fogging. Thus, two-part, curing formulations have been avoided, since curing reactions may evolve volatile byproducts. The mastic should be UV stable, since it will be directly exposed to UV radiation throughout its useful life. U.S. Pat. No. 5,510,416 describes a particular hot melt thermoplastic mastic. The hot melt mastic of U.S. Pat. No. 5,510,416 forms a coating on the interior of the U-shaped spacer of the IGU, so as to be retained thereon, to avoid the problem of sagging and to prevent separation of the hot melt mastic from the spacer.
Another approach to providing desiccating materials in the interior space of IGUs is the DESI-ROPE(copyright) continuous desiccating cord. Such cord is provided in continuous, pre-extruded lengths, for insertion into the spacer during manufacture of the IGU. The DESI-ROPE(copyright) is believed to be a cured EPDM elastomeric material impregnated with a desiccant. This product avoids some of the problems associated with the thermoplastic compositions, but comes with its own set of drawbacks. Since the cord is pre-manufactured and contains desiccant, it must be handled and stored appropriately between the times of manufacture and use so as to avoid premature moisture adsorption and saturation. According to the manufacturer""s information, reels of the DESI-ROPE(copyright) material are supplied in vacuum-sealed, moisture-proof foil bags which are in turn packaged in high density polyethylene bags, and shipped in cardboard boxes. As a result, packaging for protecting this product from inadvertent exposure to moisture is an important issue, resulting in additional costs and handling and storage precautions.
The present invention provides a method of applying a flowable, non-adhering desiccating matrix which overcomes the aforementioned problems of the prior art. The present invention also provides a flowable, non-adhering desiccating matrix formulation. The present invention further provides an efficient method for forming an insulating glass unit having a closed hollow spacer containing the thermoplastic desiccating matrix, in which method the matrix formulation may be pumped at or below the temperatures used for hot melt thermoplastics but does not adhere to the spacer when the molten desiccating matrix formulation solidifies. Thus, a preferred formulation is characterized by the combined features of being capable of being dispensed from, e.g., hot melt equipment and of being non-adhering. The feature of being dispensed by hot melt equipment allows the matrix to be used in existing hot melt equipment. In an alternative embodiment, one or two part curable desiccating mastic formulations may be used, provided such formulations do not result in an undue amount of evolved water or VOCs which could result in fogging. In such an alternative embodiment, the curable material may be pumped at room or ambient temperature. A two part formulation would be statically mixed at the point of application to the spacer. This alternative formulation, like the other formulations disclosed herein, preferably is non-adhering to the surfaces of the spacer when solidified.
The non-adhesion feature of the invention essentially allows the entire surface of the desiccating matrix to be exposed to the atmosphere in the interior space of the IGU. As a result of the increased surface area, the inventive thermoplastic desiccating matrix formulation features enhanced adsorption of moisture and volatile elements, thus contributing to a superior IGU which is easy to manufacture.
According to one aspect of the invention, a closed hollow spacer for an insulating glass unit, is made by (1) dispensing a flowable desiccating matrix formulation onto a portion of the spacer which will be inside the hollow spacer when the spacer has been closed; (2) allowing or causing the formulation to solidify into a solid matrix that will be detached from the spacer; and (3) closing the spacer whereby the detached solid matrix will be retained within the spacer.
According to another aspect of the invention, an insulating glass unit is made by assembling the closed spacer between two panes of glass. An adhesive material may be provided between the spacer and the panes of glass, and a sealing material may be provided between the spacer and/or the panes of glass.
In one embodiment, the invention provides a method of making a closed hollow spacer for an insulating glass unit, comprising (1) dispensing a flowable desiccating matrix formulation onto a portion of the spacer which will be inside the spacer when the spacer has been closed; (2) allowing or causing the formulation to solidify into a solid matrix and to detach from any attachment to the spacer; (3) closing the spacer whereby the detached matrix will be retained within the spacer.
In one embodiment, the invention provides a method of making an insulating glass unit including at least two glass panels and a hollow spacer having an interior wall and separating the glass panels to form an interior space of the IGU, the hollow spacer retaining therein a desiccating matrix, comprising: (1) heating a desiccating matrix formulation to a temperature at which it is flowable; (2) dispensing the heated formulation onto the interior wall of the hollow spacer; (3) allowing the formulation to solidify to form a solid matrix; and (4) freeing the matrix from any adhesion to the spacer. The matrix may be freed from adhesion to the spacer by cooling or other means, such as by mechanically dislodging the solid matrix from any adhesion to the spacer.
In one embodiment, the invention provides a method of making an insulating glass unit including at least two glass panels and a hollow spacer separating the glass panels, the panels and spacer forming an interior space of the IGU, the hollow spacer retaining therein a solid desiccating matrix, comprising: (1) heating a desiccating matrix formulation to a temperature at which it is flowable; (2) dispensing the heated formulation into the hollow spacer under conditions such that it forms a solid matrix which does not adhere to the spacer in use.
In one embodiment, the invention provides a thermoplastic desiccating matrix formulation including about 80 to about 30 weight % of the formulation of a thermoplastic material, wherein the thermoplastic material is selected from the group consisting of ethylene vinyl acetate copolymer, LLDPE, LDPE, styrenic thermoplastic elastomer, ethylene-methyl acrylate copolymer, and ethylene-acrylic acid copolymer; and about 20 to about 70 weight % of the formulation of an adsorbent component, wherein the adsorbent component includes a moisture adsorbing material and a volatile organic chemical adsorbing material, of which 0-50% of the adsorbent component is the adsorbent of volatile organic compounds.
In one embodiment, the invention provides a thermoplastic desiccating matrix formulation which, when dispensed as a flowable liquid onto an inner surface of an edge assembly and allowed to cool to ambient temperature, forms a solid matrix having an outer surface which does not adhere to the inner surface of the edge assembly.
In one embodiment, the invention provides a thermoplastic desiccating matrix formulation comprising about 50 weight % of the formulation of an ethylene vinyl acetate copolymer; and about 50 weight % of the formulation of an adsorbent component.
In one embodiment, the invention provides a desiccating matrix formulation consisting essentially of a combination of about 50 weight % of an ethylene vinyl acetate copolymer containing about 14 weight % of vinyl acetate, and about 50 weight % of the formulation of a mixture containing about 85 weight % of 3A molecular sieve and about 15 weight percent of 13X molecular sieve.
In one embodiment, the invention provides a desiccating matrix formulation comprising about 80 to about 30 weight % of the formulation of a curable material, wherein the curable material is selected from the group consisting of a one-part mixture comprising an isocyanate-terminated prepolymer and dibutyl tin dilaurate; a two-part mixture in which a first part comprises an isocyanate-terminated prepolymer and dibutyl tin laurate and a second part comprises an active hydrogen compound; and a two-part mixture in which a first part comprises diglycidyl ether bisphenol A and a second part comprises an epoxy curative; and about 20 to about 70 weight % of the formulation of an adsorbent component, wherein the adsorbent component includes a moisture adsorbing material and a volatile organic chemical adsorbing material, of which 0-50% of the adsorbent component is the adsorbent of volatile organic compounds.
The foregoing and other features of the invention are hereinafter more fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.